I want to give some additional information if you want to round off your result you can use

use Math::Round;
$data=nearest (.1,$data)
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With use of this class and this function you can round off upto desired decimal number,where $data is some number we are getting to which we want to round off and Your problem is solved i think so ,it is because you are using "," instead of "."
I think it will help you in future.